Influence of Heat Treatment on the Autocatalytic Ni-P and Ni-Co-P Deposits

A. Ahmad, K.M. Ghauri, L. Ali, A. A. Noshahi, J. P. G. Farr


Autocatalytic or electroless deposition is the process of depositing a coating by means of a reducing agent in solution without using electric current. Deposits so produced are primarily alloys of metal(s) with a non-metal like phosphorus or boron. Addition of a non-metal in the metallic lattice may change the metallic crystalline structure to amorphous or microcrystalline that in turn affects the properties such as wear resistance, hardness and corrosion resistance. This paper presents the electroless deposition of Ni-P and Ni-Co-P films using hypophosphite-based baths. The effects of plating parameters like bath composition, temperature, pH and heat treatment at different temperatures have been discussed. The deposits were explored for their magnetic and electrochemical behaviour. The chemical analysis of the deposits was carried out using energy dispersive X-ray analysis (EDX) and TEM. The crystal structure was determined using X-ray diffraction analysis (XRD). The magnetic properties were measured with the help of a vibrating sample magnetometer (VSM). A potentiostat was used to carry out linear sweep voltametery. The results showed that the bath temperature and the pH strongly affect the chemical composition and characteristics of the deposits. The deposits are microcrystalline in the as-deposited condition and recrystallize at 300- 3500 o C. However, the corrosion resistance of the deposits decreased after the heat treatment due to formation of different anodic phases.

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